calculate geo bounds (#8321)

Signed-off-by: Kerry Archibald <kerrya@element.io>

src/utils/beacon/bounds.ts

@@ -0,0 +1,56 @@
+/*
+Copyright 2022 The Matrix.org Foundation C.I.C
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+import { Beacon } from "matrix-js-sdk/src/matrix";
+
+import { parseGeoUri } from "../location";
+
+export type Bounds = {
+    north: number;
+    east: number;
+    west: number;
+    south: number;
+};
+
+/**
+ * Get the geo bounds of given list of beacons
+ *
+ * Latitude:
+ * equator: 0, North pole: 90, South pole -90
+ * Longitude:
+ * Prime Meridian (Greenwich): 0
+ * east of Greenwich has a positive longitude, max 180
+ * west of Greenwich has a negative longitude, min -180
+ */
+export const getBeaconBounds = (beacons: Beacon[]): Bounds | undefined => {
+    const coords = beacons.filter(beacon => !!beacon.latestLocationState)
+        .map(beacon => parseGeoUri(beacon.latestLocationState.uri));
+
+    if (!coords.length) {
+        return;
+    }
+
+    // sort descending
+    const sortedByLat = [...coords].sort((left, right) => right.latitude - left.latitude);
+    const sortedByLong = [...coords].sort((left, right) => right.longitude - left.longitude);
+
+    return {
+        north: sortedByLat[0].latitude,
+        south: sortedByLat[sortedByLat.length - 1].latitude,
+        east: sortedByLong[0].longitude,
+        west: sortedByLong[sortedByLong.length -1].longitude,
+    };
+};